design features and commissioning of the 700 mw coal-fired boiler

Mitsubishi Heavy Industries, Ltd.Technical Review Vol.38 No.3 (Oct. 2001)

106

Design Features and Commissioning of the 700 MW Coal-FiredBoiler at the Tsuruga Thermal Power Station No. 2

Susumu Sato*1 Masahiko Matsuda*1Takao Hashimoto*2 Yoshiyuki Wakabayashi*2

Akira Hashimoto*3

*1 Power Systems Headquarters*2 Nagasaki Shipyard & Machinery Works*3 Nagasaki Research & Development Center, Technical Headquarters

The 700 MW coal-fired supercritical sliding pressure boiler at Hokuriku Electric Power Co., Inc., TsurugaThermal Power Station No.2 was designed based on the high-performance and reliable 500 MW boiler at thesame Power Station No.1. Applying elevated steam of 593/593 OC, our state-of-the-art low-NOx combustion A-PM burner, A-MACT and MRS pulverizer technology, this boiler has achieved the highest combustion performancewith extremely low NOx emission and unburnt carbon together with outstanding boiler operation. This paperreports the design features and operation results of the boiler, e.g., (1) extremely low NOx and unburnt carbondue to cutting-edge combustion and (2) superior boiler operating performance and minimum 15% load in exclusivecoal firing.

1. Introduction1. Introduction1. Introduction1. Introduction1. IntroductionThe 700 MW boiler at Hokuriku Electric Power Co.,

Inc., Tsuruga Thermal Power Station No.2, plannedand installed as a latest coal-fired supercritical slid-ing pressure operation once-through boiler for vari-ous kinds of coal, started commercial operation onSept. 28, 2000, after smooth commissioning. Thisboiler not only utilizes experience gained in the in-stallation and operation of the existent 500 MWboiler(1) at the Power Station No.1, but also employsadvanced technology developed by Mitsubishi HeavyIndustry Ltd. (MHI) so as to operate at high-efficiencywith various coals, under intermediate load operation,and possess the environmental protection, etc. re-quired for coal-fired power generation in the new cen-tury. This report introduces the features and theoperational data of this boiler.

The major features in the design are as follows:(1) Ensured reliability by following the basic design

concepts of the existent 500 MW boiler which hasdemonstrated high-performance and reliability

( 2 ) H i g h t e m p e r a t u r e s t e a m c o n d i t i o n s(24.1 MPa X 593/593OC) and high efficiencies overthe whole load range by using sliding pressure op-eration

(3) High reliability in the high temperature steam con-dition boiler by applying new materials (Ka-S U S 3 1 0 J 1 T B , K a - S U S 3 0 4 J 1 H T B ,Ka-SUS410J3TB/TP(2), Ka-STBA24J1(2)) with excel-lent in anti-high temperature corrosion, anti-steamoxidation, and high temperature strength properties

(4) Usable with various kinds of coal (128 kinds ofdesign coals)

(5) Extremely low NOx (less than 150 ppm) combus-tion by employing A-PM (Advanced-Pollution Mini-

mum) burners(3) and a new A-MACT (Advanced-Mitsubishi Advanced Combustion Technology)

(6) Reduced unburnt carbon in fly ash (less than 5%)and minimum load in exclusive coal firing (15%ECR) by employing an MRS (Mitsubishi RotarySeparator) pulverizer equipped with a two-stageseparator consisting of rotary and fixed type.

(7) Simplified facility and reduced auxiliary power

Fig. 1 Boiler general arrangement side viewFig. 1 Boiler general arrangement side viewFig. 1 Boiler general arrangement side viewFig. 1 Boiler general arrangement side viewFig. 1 Boiler general arrangement side viewArrangement of heating tubes, major auxiliaries, burners, draftair duct and flue gas duct are shown.

Table 2 Used coal propertiesTable 2 Used coal propertiesTable 2 Used coal propertiesTable 2 Used coal properties Lemington

coal Workworth

coal Satui coal Blair athol

coal Higher heating value AR (As Received) kJ/kg 29 220 29 530 28 760 28 470

Total moisture AR (As Received) wt % 8.2 9.8 10.0 17.7 Inherent moisture AD (Air Dry) wt % 2.8 3.5 5.5 6.2

Fixed carbon AD (Air Dry) wt % 49.7 51.9 43.0 57.1 Volatile matters AD (Air Dry) wt % 34.3 34.3 44.5 28.5

Proximate analysis

Ash AD (Air Dry) wt % 13.2 10.3 7.0 8.2 Fuel ratio 1.45 1.51 0.97 2.00

Carbon Dry wt % 72.80 75.14 74.16 74.21 Oxygen Dry wt % 6.69 7.49 10.81 10.51

Hydrogen Dry wt % 4.81 4.98 5.85 4.49 Nitrogen Dry wt % 1.54 1.70 1.30 1.61

Ultimate analysis

Total sulfur Dry wt % 0.36 0.42 0.53 0.42 Grindability HGI 48 50 40 59


107

consumption by using a secondary pass distribu-tion damper as a reheater steam temperature con-trol system

(8) Improved control functions by employing the lat-est overall control system; DIASYS-SEP (DigitalIntelligent Automation System-Software EnrichedProcessor), such as the boiler automatic control,mill/burner automatic control, etc.

(9) Reduced construction period by applying the SBS(Steel Structure Boiler Simultaneous Construction)construction method suitable for small area

2. Measures for use of various kinds of coal and for2. Measures for use of various kinds of coal and for2. Measures for use of various kinds of coal and for2. Measures for use of various kinds of coal and for2. Measures for use of various kinds of coal and forelevated steam temperature conditionselevated steam temperature conditionselevated steam temperature conditionselevated steam temperature conditionselevated steam temperature conditions

The major specifications of this boiler are shown

in TTTTTablablablablableeeee 11111. The side view is shown in FigFigFigFigFig..... 11111.Four kinds of coal shown in TTTTTablablablablableeeee 22222 were used dur-

ing commissioning. The furnace size was designed tobe basically similar to the No.1 boiler, taking intoconsideration firing the various coals (128 kinds) andenabling mixed firing with sub-bituminous coal.

In order to cope with a high steam temperature upto 593/593OC, high temperature strength materialswere adopted for the pressure parts to ensure reli-ability. The following new materials were chosen:18Cr steel (Ka-SUS304J1HTB) and 25Cr steel (Ka-SUS310J1TB) for the high temperature heating tubesof the superheater and reheater, 2Cr steel (Ka-STBA24J1) and 12Cr steel (Ka-SUS410J3TB) for thehigh temperature non-heating tubes, and 12Cr steel

Table 1 Boiler major specificationsTable 1 Boiler major specificationsTable 1 Boiler major specificationsTable 1 Boiler major specifications Boiler type Mitsubishi supercritical sliding pressure operation once-through boiler radiant reheat

type (indoor type) Furnace type Spiral tube type hopper bottom single furnace

Steam flow rate Main steam 2 120 000 kg/h Steam pressure Superheater outlet 25.0 MPa

At maximum continuous load (MCR) Steam temperature

Superheater outlet Reheater outlet

597OC 595OC

Fuel Coal, A-oil (25% MCR capacity) Combustion system (NOX-reduction method) Circular firing system (A-PM burner + new A-MACT method) Pulverized coal-firing system Unit direct pressurizing method Draft system Balanced draft system Primary air draft system Cold primary air fan method Heat recovery method for start Boiler water circulation pump system Steam temperature control range

Main steam Reheat steam

From MCR up to 30% load From MCR up to 50% load

Steam temperature control system

Main steam Reheat steam

Feed water/fuel ratio, spray Gas distributing damper, excess air ratio, spray (at load change, for emergency)

Coal pulverizer Mitsubishi MRS: 6 sets Forced draft fan Variable blade pitch axial flow type: 2 sets Primary air draft fan Variable blade pitch axial flow type: 2 sets Induced draft fan Variable blade pitch axial flow type: 2 sets Air preheater Regenerative type: 2 sets

Major auxiliaries

DeNOx system Dry catalytic NOx removal system: 2 sets


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(Ka-SUS410J3TP) for the main steam pipes and hightemperature reheater steam pipes.

3. Measures for extremely low NOx combustion and3. Measures for extremely low NOx combustion and3. Measures for extremely low NOx combustion and3. Measures for extremely low NOx combustion and3. Measures for extremely low NOx combustion andreduction of unburnt carbon in fly ashreduction of unburnt carbon in fly ashreduction of unburnt carbon in fly ashreduction of unburnt carbon in fly ashreduction of unburnt carbon in fly ash

The latest low NOx and low unburnt carbon com-bustion system combined with an A-PM burner, newA-MACT in-furnace DeNOx method, and MRS pulver-izer with a two-stage separator was adopted. Thissystem was first commercially employed in the 1 000MW boiler at Chugoku Electric Power Co. , Inc.Misumi Thermal Power Station No.1(4) to reduce NOxand unburnt carbon in fly ash.(1) A-PM burner

The A-PM burner is MHI's most advanced low NOxburner not only realizing an even lower NOx in com-parison to the conventional continuous wind box typePM burner, it also reduces the number of the windbox dampers and improves the accessibility to theburner part by making the wind box a split type, andtherefore a simple structure with excellent maintain-ability, reliability, and durability (FigFigFigFigFig..... 22222).

Although a PM burner reduces NOx by separatingthe flames into the conc. flames with a high coal-airratio and weak flames with a low coal-air ratio, theA-PM burner reduces NOx by forming a single flamecoaxially composed of a conc. peripheral part and aweak core part simultaneously maintaining ignitionstability by the peripheral conc. part. In other words,it is intended to improve the ignition performance asa whole burner, form a NOx reducing zone having alow air ratio at a higher temperature, and realize anextremely low NOx combustion by utilizing both theburner by itself, and the whole furnace in combina-tion with additional air described later.(2) New A-MACT in-furnace DeNOx process

The new A-MACT process shown in FigFigFigFigFig..... 33333 is in-

tended to further reduce NOx by the same amount asunburnt carbon. It employs the multi-additional air(AA) feeding method having air ports provided at twostages, in each furnace corner for the lower stage andeach wall center for the upper stage, to complete burn-ing, and therefore the mixing of the AA and flames ispromoted and the burning-off performance of unburntcarbon is improved in comparison to the conventionalsingle stage AA feeding.(3) MRS pulverizer

This boiler is provided with a MRS pulverizer re-alizing stable production of even finer pulverized coalby two-stage separator having fixed type separatorintegrated with a conventional MRS pulverizer(5) re-alizing a greater fineness by rotary separator aloneand demonstrating a high performance in the No. 1boiler. (FigFigFigFigFig..... 4.4.4.4.4.)

As shown in FigFigFigFigFig..... 55555, the MRS pulverizer can remark-ably reduce coarse particles of 100 mesh (149m) or

Conc. flameWeak flameConc. flame

A-PM burner

(Upper stage AA)

Upper stage AA

Lower stage AA

Unburnt carbon-burning

completion zone

NOx removal zone

Main burner burning zone

(Lower stage AA)

AA is fed from multiple directions in two stages to improve

unburnt carbon-burning-off performance.

NOx is reduced by reducing agent produced at the main burners.

A-PM burners with excellent burning and ignition performance are adoptedfor the main burners, so that the production of the NOx-reducing agent is promoted by the formation of a reduction atmosphere.

Fixed type separator

Rotary separator

Mixed flow of coarse and fine particles

Coarse particles Raw coal

Pulverized coal

Fig. 2 Outline drawing of A-PM burnerFig. 2 Outline drawing of A-PM burnerFig. 2 Outline drawing of A-PM burnerFig. 2 Outline drawing of A-PM burnerFig. 2 Outline drawing of A-PM burnerThe A-PM burner has low NOx performanceand excellent ignition stability. The burnerhas excellent maintainability, reliability, anddurability because of its simple structure.

Fig. 3 New A-MACT in-furnace DeNOx systemFig. 3 New A-MACT in-furnace DeNOx systemFig. 3 New A-MACT in-furnace DeNOx systemFig. 3 New A-MACT in-furnace DeNOx systemFig. 3 New A-MACT in-furnace DeNOx systemAdditional air (AA) is fed from multiple directions in two stagesto improve the unburnt carbon-burning-off performance andreduce NOx emissions.

Fig. 4 MRS pulverizerFig. 4 MRS pulverizerFig. 4 MRS pulverizerFig. 4 MRS pulverizerFig. 4 MRS pulverizerCoarse particles after separation are uniformlymixed with raw coal by the two-stage separatorconsisting of both rotary and fixed typeseparators, so that mill vibration at the highfineness zone is reduced.

2.0

1.5

1.0

0.5

065 70 75 80 85 90 95 100Stable operation zone of single stage separator MRS pulverizer

Stable operation zone of two-stage separator MRS pulverizer

Ratio

of 1

00 m

esh

resid

ues

(-)

Ratio of 200 mesh residues (%)

Fixed type sepa-rator (pulverizer)

MRS pulverizer (single stage separator)

MRS pulverizer (two-stage separator)

95

90

85175 350 525 700

Load (MW)

Boile

r effic

iency

(%)

: Design or guarantee value: Measured value


109

larger that plays the dominant role in increasingunburnt carbon. However, because coarse particlesseparated by the rotary separator pile on the raw coalon the grinding table, slip vibration occurs when thecoarse particles are caught between the rollers, caus-ing the stable operation to be hard to maintain at ahigh fineness. Therefore, the fixed type separator isintegrated to return the coarse particles to the cen-ter of the table and mix them with raw coal, so thatthe mill vibration can be controlled to ensure stableoperation even at a high fineness containing fine par-ticles with 90% or more passing 200 mesh.(4) Realization of low NOx and low unburnt carbon in

fly ashThe combustion performance of low NOx and low

5.0

4.0

3.0

2.0

1.0

0.050 100 150 200

NOx (ppm: 6% O2)

: Data of a conventional PM burner

Unbu

rnt c

arbo

n in

fly a

sh (%

)

Low fuel ratio coalHigh fuel ratio coal

: Data of A-PM burner (other boilers): Data of A-PM burner (Tsuruga No. 2)

unburnt carbon in fly ash is remarkably superior tothe combination of the conventional PM burner andMRS pulverizer (FigFigFigFigFig..... 66666) and also an excellent low O2combustion performance is demonstrated such thatlow excess air operation of 15% or less (FigFigFigFigFig..... 77777) can beperformed at 100% load.

4. Boiler performance4. Boiler performance4. Boiler performance4. Boiler performance4. Boiler performanceThe boiler efficiencies based on the performance

test results are shown in FigFigFigFigFig..... 88888.The unburnt carbon loss was reduced and the low

excess air operation was realized by the combinationof the A-PM burner, new A-MACT, and MRS pulver-izer. This resulted in excellent measured boiler effi-ciencies completely exceeding the guarantee or designfigures over the whole load range from 100% load upto a minimum load of 15%. These results guaranteedthe high efficiency operation of the whole plant.

For the steam temperature characteristics, the pre-dicted main steam and reheat steam temperaturescould be maintained over the whole load range for allused coals, within the suitable ranges of controllingparameters for the SH spray and gas distributiondamper.

Fig. 5 Fineness of pulverized coalFig. 5 Fineness of pulverized coalFig. 5 Fineness of pulverized coalFig. 5 Fineness of pulverized coalFig. 5 Fineness of pulverized coalThe MRS pulverizer with the two-stage separator iscapable of stable operation at a high fineness zone.

Fig. 6Fig. 6Fig. 6Fig. 6Fig. 6

Extremely low NOx emissions and low unburnt carbonin fly ash were demonstrated by the combination of theA-PM burner, new A-MACT, and MRS pulverizer.

Fig. 7 Low excess air performanceFig. 7 Low excess air performanceFig. 7 Low excess air performanceFig. 7 Low excess air performanceFig. 7 Low excess air performanceExcellent combustion stability and low excess air combustionwere realized.

Fig. 8 Boiler efficiency at performance testFig. 8 Boiler efficiency at performance testFig. 8 Boiler efficiency at performance testFig. 8 Boiler efficiency at performance testFig. 8 Boiler efficiency at performance testHigh efficiency operation over the whole load rangewas realized by achieving low excess air ratio and lowunburnt carbon.

80

60

40

20

0 175 350 525 700Load (MW)

Exce

ss a

ir ra

tio a

t ECO

outle

t (%) : Design value

: Measured value for Workworth coal: Measured value for Satui coal: Measured value for Blair Athol coal

Measured NOx emissions and unburntMeasured NOx emissions and unburntMeasured NOx emissions and unburntMeasured NOx emissions and unburntMeasured NOx emissions and unburntcarbon in fly ashcarbon in fly ashcarbon in fly ashcarbon in fly ashcarbon in fly ash


110

Introducing a new control method(6) applied to vari-ous kinds of coal by fuzzy logic for presuming the fur-nace conditions and heating surface conditions, anexcellent controllability was confirmed during com-missioning with four used coals chosen for theirwidely diverging properties.

It was also confirmed that exclusive coal firing at15% minimum load can be achieved with operatingstably, automatically, and continuously.

5. Load swing and unit start-up characteristics5. Load swing and unit start-up characteristics5. Load swing and unit start-up characteristics5. Load swing and unit start-up characteristics5. Load swing and unit start-up characteristicsT h e A P C w a s a d j u s t e d i n f o u r l o a d b a n d s

(530 MW 700 MW for Band I, 380MW 560MWfor Band II, 315MW 420MW for Band III, and210MW 315MW for Band IV) and in load changingrate (4%/min for Bands I to III and 2%/min for BandIV). The deviation in the unit outputs, steam pres-sures, and steam temperatures were controlled withinthe prescribed figures by the application of the latestoverall control system, DIASYS-SEP, so that the goodresults were obtained.

Also, in the unit start-up tests, the unit could bestarted up within the planned time for each start-upmode, and also it was confirmed that the unit is ca-pable of hot start-up with stopping BRP (boiler waterrecirculation pump) without any problem.

6. SBS construction method6. SBS construction method6. SBS construction method6. SBS construction method6. SBS construction methodBecause this boiler needed to be installed in a small

area and therefore the large-scale zone module con-struction(7) could not be applied, the SBS construc-tion method was adopted. In this method, the mainpiping, ducts, and pulverized coal piping were in-stalled in parallel with steel structure erections, andthen the main ceiling beams and the upper pressur-ized parts were lifted and installed as one block.

The adoption of this method extended the scope ofmodules and blocks assembled in shop and enabledthe application of "just-in-time" physical distributionmanagement, thereby reducing the marshalling inyard, mitigating traffic jams by reducing in person-nel and accommodations, relieving congestion whileunloading by reducing of the number of assigned ves-sels, and leveling the site work, the construction pe-riod could be shortened to 22 months, from the firststeel structure erection to the initial firing, and si-multaneously work safety could be improved by thereduction of elevated work at site.

7. Conclusion7. Conclusion7. Conclusion7. Conclusion7. ConclusionThe Tsuruga No. 2 boiler demonstrated its excel-

lent environmental adaptability, boiler static char-acteristics and combustion performance achieving thelowest levels of O2 combustion, NOx, and unburntcarbon. This was achieved by using a design conceptsimilar to the existent No. 1 boiler, which had alreadydemonstrated high performance and reliability andadditionally by the effective combination of a elevatedsteam temperature and the latest technology (suchas the A-PM burner, new A-MACT, and MRS pulver-izer). Furthermore, from the point of view of opera-tion, excellent middle load operation includingexcellent capability to fire various coals, the dynamicperformance, the start-up performance, and the mini-mum load operation were verified.

MHI utilizes the previous experience obtainedthrough the completion of the Tsuruga No. 2 boiler tofuture designs and also intends to work continuouslyto further develop and improve technology requiredby the world.

Finally, the authors would like to express our grati-tude to the persons concerned of Hokuriku ElectricPower Co., Inc. for their courteous guidance and co-operation given to us over the whole period from thebasic design through to the commissioning.

ReferencesReferencesReferencesReferencesReferences(1) Nakajima, F., et al., Field Performance of 500 MW Advanced

Coal Fired Supercritical Sliding Pressure Operation Boilerfor Unit No. 1 of Tsuruga Thermal Power Station, HokurikuElectric Power Co, Inc., Mitsubishi Heavy Industries Tech-nical Review Vol. 29 No. 3 (1992)

(2) Komai, N., et al., Field Evaluation Test of Newly DevelopedBoiler Tubing Steels, Mitsubishi Juko Giho Vol.34 No.2(1997)

(3) Kaneko, S., et al., Development of Pulverized Coal Fired LowNOx Advanced PM Burner, Mitsubishi Juko Giho Vol.32 No.1(1995)

(4) Kaneko, S., et al., Design and Operation Experience of a 1 000MW Ultra Supercritical Coal Fired Boiler with Steam Con-dition of 25.4 MPa 604/602OC, Mitsubishi Heavy IndustriesTechnical Review Vol.36 No.3 (1999)

(5) Kawamura, T., et al., New Approach to NOx Control Optimi-zation of NOx and Unbunt Carbon Losses, the 1989 JointSymposium on Stationary Combustion NOx Control, EPRI

(6) Moriyama, I., et al., Development of New Control Technol-ogy for Multi-Coal Fired Boiler, Mitsubishi Juko Giho Vol.35No.1 (1998)

(7) Takahashi, T., et al., Zone Module Construction Method forLarge Coal-Fired Power Plant, Mitsubishi Heavy IndustriesTechnical Review Vol.32 No.3 (1995)

design features and commissioning of the 700 mw coal-fired boiler

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